The present invention relates to a print head in which print wires are moved to a printing position by swinging armatures by means of energized coils, and more particularly, to an armature supporting structure thereof.
Conventionally, in some conventional print heads of this type, a plurality of armatures are swingably supported on a head body by means of leaf springs, individually, and print wires are moved to a printing position by swinging the armatures.
In these conventional print heads, however, the armatures are supported with the aid of the leaf springs, which are bound to suffer a prolonged high-order vibration, after the printing wires strike against printing paper, or after they return to a rest position after printing operation. Thus, it takes the leaf springs much time to be restored to their original position. As a result, the printing cycle becomes too long for high-speed printing.
Some arrangements have been proposed as a measure to counter the high-order vibration. In one such arrangement, as shown in FIG. 8, the proximal end portion of each of armatures 1 is swingably mounted on a head body 3 by means of a pair of torsion bars 2, for use as resilient members. Each armature 1 is swung by energy which is accumulated by a twist of the torsion bars 2. By doing this, one of print wires 4, which are fixed individually to the free end portions of the armatures, is moved to the printing position.
In the prior art print head constructed in this manner, however, each armature 1 is supported only by a pair of torsion bars 2, so that the bar 2 are subjected to stress concentration. Thus, the torsion bars 2 are lowered in durability, so that the life of the print head is shortened.